Interpretive Summary: Oxbow lakes in the Mississippi Delta as recreational resources have decreased as water quality and fisheries have declined. Three watersheds with oxbow lakes were selected and developed with different levels of best management practices (BMPs). Water quality within the lakes was examined from before and after best management practices. Analyses of water quality prior to the implementation of BMPs indicated lakes that were ecologically stressed due to excessive in-flowing sediments. The most dramatic improvements in water quality were realized through the use of conservation tillage, winter cover crops, and grade control BMPs. Sediments were decreased while water clarity and chlorophyll increased. Reducing suspended sediment concentrations in these oxbow lakes resulted in conditions favorable for plankton production. Increases in plankton production improve fish productivity. These results will be useful to extension personnel, action agencies involved in water quality planning, and to farmers.

Technical Abstract:
This paper examined and documented pre-management water quality conditions on three oxbow lakes and discussed resulting changes following the implementation of Best Management Practices within the Mississippi Delta Management Systems Evaluation Area (MSEA). Experimental design of the Mississippi Delta MSEA called for the development of structural and cultural treatments to reduce sediment and associated pollutants entering watershed oxbow lakes. Three watersheds within the project were selected and developed with different levels of best management practices (BMPs). Changes in lake water quality and fisheries characteristics were used as measures of management success. Analyses of water quality prior to the implementation of BMPs indicated lakes that were stressed and ecologically damaged due to excessive in-flowing sediments. Significant improvements in water quality were realized through the use of cultural and structural BMPs. Sediments were decreased 34 to 59%, while Secchi visibility and chlorophyll generally increased. The most dramatic improvements in water quality occurred in the two watersheds that featured cultural practices and combinations of cultural and structural practices, respectively. Reducing suspended sediment concentrations in these oxbow lakes resulted in conditions favorable for phytoplankton production. Increases in phytoplankton production resulted in increased chlorophyll concentrations and higher concentrations of dissolved oxygen, leading to improved secondary productivity. Results further indicated that cultural BMPS may play the more vital role in improving lake water quality and may be needed in addition to structural measures to ensure improved water quality in oxbow lakes receiving agricultural runoff.